1. Technical Field
The present invention relates to a color processing apparatus and method, and a storage medium storing a color processing program. More particularly, the present invention pertains to a color processing apparatus having a color gamut converting unit for converting color gamuts of input image data according to a set color gamut converting condition by setting the color gamut converting condition so that a color gamut of image data in a predetermined color space may fall within an output color gamut without depending on any particular device, a color processing method usable with the color processing apparatus, and a storage medium storing color processing program causing a computer to function as the color processing apparatus.
2. Background Art
Color gamuts reproducible by image output devices such as color printers or displays, or color gamuts read in by image input devices such as scanners are different from each other and depend on the type or model of the devices, and for example, when printing out with a color printer an image that has been displayed on a display, if image data for displaying an image on a display is directly output to a color printer, the color of images reproduced in the two devices is differ significantly depending on the difference between the color gamuts of the devices. As a technology for improving the difference in color reproduction, for example, it has been hitherto proposed to carry out conversion of color gamuts to replace colors in a device-independent color space that is not dependent on any specific device (for example, uniform sensory color space such as L*a*b* color space recommended by CIE (Commission Internationale de l'Eclairage), color space of tristimulus value CIEXYZ display color system, or CAM color space specified by color visible model such as CIAMAM02 (Colour Appearance Model 2002) with colors in the color gamut of the image data output device (also called Gamut mapping).
A first aspect of the present invention provides a color processing apparatus including a color gamut conversion unit, a setting unit and a pre-processing unit. The color gamut conversion unit sets, on the basis of output color gamut information expressing an output color gamut in a predetermined color space not depending on a specific device, a color gamut conversion condition for converting image data according to a specified conversion rule so that the color gamut of image data in the predetermined color space falls within the output color gamut, and carrying out color gamut conversion of input image data according to the set color gamut conversion condition. The setting unit sets a limiting condition for the color gamut conversion. The pre-processing unit changes the color value of specified color(s) so that the color value of the specified color(s) out of the input image data are converted by color gamut conversion by the color gamut conversion unit to an output corresponding color satisfying the limiting condition set through the setting unit, and for pre-processing so as to change the color values of colors other than the specified color(s) of the input image data according to the relationship between the color value before change of the specified color(s) and the color value after change of the specified color(s).